Anterior Interosseous Nerve

Written by Max Bidewell and Kumail Jaffery

Last updated April 21, 2024 • 10 Revisions

The anterior interosseous nerve is a motor branch of the median nerve.

It supplies the deep muscles of the anterior forearm – flexor pollicis longus, lateral half of flexor digitorum profundus and pronator quadratus.

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Course

The anterior interosseous nerve arises from the median nerve in the proximal forearm, between the heads of the pronator teres.

It descends down the forearm, between the flexor pollicis longus and the flexor digitorum profundus. It is accompanied by the anterior interosseous artery.

At the level of the wrist, the anterior interosseous nerve passes deep to the pronator quadratus and terminates as small sensory branches.

Fig 1
Course of the anterior interosseous nerve, a branch of the median nerve.

Sensory Functions

The anterior interosseous nerve terminates as articular branches that contribute to sensation at the distal radioulnar, radiocarpal, and intercarpal joints.

Motor Functions

The anterior interosseous nerve supplies motor innervation the deep compartment of the anterior forearm:

  • Flexor pollicis longus
  • Lateral half of flexor digitorum profundus (index and middle fingers)
  • Pronator quadratus

Fig 2
Deep flexor muscles of the anterior forearm.

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